Papers, plastic films, metal foils, and the like have hitherto been used in wide applications inclusive of liquid materials or granular materials for various food products, chemicals, miscellaneous goods, etc., packaging materials of solids, materials for agricultural use, building materials, and the like. In particular, plastic films are excellent in terms of strength, water resistance, formability, transparency, cost, and the like and are used as bags and containers in a lot of applications. Examples of representative plastic films include those constituted of polyethylene, polypropylene, polystyrene, polyvinyl chloride, or the like. However, these resins are hardly degradable under a natural environment, and in the case of performing an incineration treatment, there is involved a problem such as generation of a noxious gas, damaging of an incinerator, etc.
In order to solve the foregoing problem, various resins have been studied. For example, there is known a technique for solving the foregoing problem by using an aliphatic polyester-based resin such as polybutylene succinate, polybutylene succinate adipate, etc., an aliphatic oxycarboxylic acid-based resin such as polylactic acid, etc., or an aromatic-aliphatic copolyester-based resin such as polybutylene adipate terephthalate, etc. (see, for example, Patent Document 1).
In addition, in an aromatic-aliphatic copolyester-based resin such as polybutylene adipate terephthalate, etc., it was known to enhance biodegradability by allowing an aliphatic unit to exist between aromatic units. However, for the purpose of improving flexibility and tensile strength, there is disclosed an aliphatic polyester-based resin composition containing an aliphatic polyester-based resin having excellent crystallinity and formability, an aromatic-aliphatic copolyester-based resin having a low content of an aromatic dicarboxylic acid component, and an aliphatic oxycarboxylic acid-based resin in a prescribed ratio (see, for example, Patent Document 2).